Cardiac output monitoring: an integrative perspective

Immediate management of a stable patient with unstable pelvis

The diagnosis of a traumatic unstable pelvis in a stable patient is a temporary concept depending on when we see the patient, as all patients presenting with hemorrhagic shock have hemodynamic stability until they become unstable. As a rule, the more unstable the pelvic fracture is, the higher the risk of bleeding and hemodynamic instability it has. Therefore, in unstable pelvic fractures, hemodynamic stability should be a diagnosis by exclusion. For bleeding detection in stable patients, an immediate one-stage contrast-enhanced CT scan is the appropriate diagnosis test; however, since CT scan radiation is always an issue, X-rays should be considered in those cases of hemodynamically stable patients in whom there is a reasonable suspicion that no unsafe bleeding is going on. Pelvic fracture classification is essential as usually there is an association between the injury mechanism, the fracture displacement, and the hemodynamic stability. Anteroposterior and, particularly, vertical traumatisms have much more proclivity to provoke major pelvic displacement and bleeding. The use of a pelvic binder, as early as possible including pre-hospital management, should be standard in high-impact blunt trauma patients independently of the trauma mechanisms. External fixation is the preferred method of stabilization in case of open fractures, and, in closed ones, when the schedule for definite osteosynthesis prolongs because of the patient's general condition. If possible, immediate percutaneous sacroiliac screw insertion for unstable pelvic fractures produce excellent results even in open fractures.

Dynamic changes of hepatic vein Doppler velocities predict preload responsiveness in mechanically ventilated critically ill patients

BACKGROUND

Assessment of dynamic parameters to guide fluid administration is one of the mainstays of current resuscitation strategies. Each test has its own limitations, but passive leg raising (PLR) has emerged as one of the most versatile preload responsiveness tests. However, it requires real-time cardiac output (CO) measurement either through advanced monitoring devices, which are not routinely available, or echocardiography, which is not always feasible. Analysis of the hepatic vein Doppler waveform change, a simpler ultrasound-based assessment, during a dynamic test such as PLR could be useful in predicting preload responsiveness. The objective of this study was to assess the diagnostic accuracy of hepatic vein Doppler S and D-wave velocities during PLR as a predictor of preload responsiveness.

METHODS

Prospective observational study conducted in two medical-surgical ICUs in Chile. Patients in circulatory failure and connected to controlled mechanical ventilation were included from August to December 2023. A baseline ultrasound assessment of cardiac function was performed. Then, simultaneously, ultrasound measurements of hepatic vein Doppler S and D waves and cardiac output by continuous pulse contour analysis device were performed during a PLR maneuver.

RESULTS

Thirty-seven patients were analyzed. 63% of the patients were preload responsive defined by a 10% increase in CO after passive leg raising. A 20% increase in the maximum S wave velocity after PLR showed the best diagnostic accuracy with a sensitivity of 69.6% (49.1-84.4) and specificity of 92.8 (68.5-99.6) to detect preload responsiveness, with an area under curve of receiving operator characteristic (AUC-ROC) of 0.82 ± 0.07 (p = 0.001 vs. AUC-ROC of 0.5). D-wave velocities showed worse diagnostic accuracy.

CONCLUSIONS

Hepatic vein Doppler assessment emerges as a novel complementary technique with adequate predictive capacity to identify preload responsiveness in patients in mechanical ventilation and circulatory failure. This technique could become valuable in scenarios of basic hemodynamic monitoring and when echocardiography is not feasible. Future studies should confirm these results.

Cardiac Output and Stroke Volume Assessments by Transthoracic Echocardiography and Pulse index Continuous Cardiac Output Monitor in Critically ill Adult Patients: A Comparative Study

PURPOSE

Bedside transthoracic echocardiography (TTEcho) is a noninvasive cardiac output (CO) monitoring method that has grown recently. However, there are questions regarding its accuracy compared to invasive methods. We aimed to evaluate the agreement and correlation of TTEcho and pulse index continuous CO (PiCCO) monitor measurements for CO and systolic volume (SV) in critically ill patients.

METHODS

This prospective experimental study included consecutive adult patients who required invasive hemodynamic monitoring admitted at an intensive care unit in the Federal District, Brazil, from January/2019 to January/2021. Correlation and agreement between SV and CO measurements by PiCCO and TTEcho were performed using the Spearman correlation and the Bland-Altman analysis.

RESULTS

The study enrolled 29 patients, with adequate TTEcho evaluations in all patients. There were very strong correlations between CO-TTEcho and CO-PiCCO (r = 0.845, P < .001) and SV-TTEcho and SV-PiCCO (r = 0.800, P < .001). TTEcho estimations for CO and SV were feasible within the limits of agreement in 96.6% (28/29) compared to PiCCO. The mean difference between CO-PiCCO and CO-TTEcho was 0.250 L/min (limits of agreement: -1.083 to 1.583 L/min, percentage error: 21.0%), and between SV-PiCCO and SV-TTEcho was 2.000 mL (limits of agreement: -16.960 to 20.960, percentage error: 24.3%). The reduced cardiac index (CI) measurements by TTEcho showed an accuracy of 89.7% (95% IC: 72.6%-97.8%) and an F1 score of 92.7% (95% IC: 75.0%-98.0%), considering the CI-PiCCO as the gold standard.

CONCLUSION

Echocardiographic measurements of CO and SV are comparable to measurements by PiCCO. These results reinforce echocardiography as a reliable tool to evaluate hemodynamics in critically ill patients.

Mock circulatory loop generated database for dynamic characterization of pressure-based cardiac output monitoring systems

Pulse contour cardiac output monitoring systems allow real-time and continuous estimation of hemodynamic variables such as cardiac output (CO) and stroke volume variation (SVV) by analysis of arterial blood pressure waveforms. However, evaluating the performance of CO monitoring systems to measure the small variations in these variables sometimes used to guide fluid therapy is a challenge due to limitations in clinical reference methods. We developed a non-clinical database as a tool for assessing the dynamic attributes of pressure-based CO monitoring systems, including CO response time and CO and SVV resolutions. We developed a mock circulation loop (MCL) that can simulate rapid changes in different parameters, such as CO and SVV. The MCL was configured to simulate three different states (normovolemic, cardiogenic shock, and hyperdynamic) representing a range of flow and pressure conditions. For each state, we simulated stepwise changes in the MCL flow and collected datasets for characterizing pressure-based CO systems. Nine datasets were generated that contain hours of peripheral pressure, central flow and pressure waveforms. The MCL-generated database is provided open access as a tool for evaluating dynamic characteristics of pressure-based CO algorithms and systems in detecting variations in CO and SVV indices. In an example application of the database, a CO response time of 10 s, CO and SVV resolutions with lower and upper limits of (-9.1%, 8.4%) and (-5.0%, 3.8%), respectively, were determined for a pressure-based CO benchtop system. This tool will support a more comprehensive assessment of pressure-based CO monitoring systems and algorithms.

A bedside ultrasound protocol to the measurement of the systemic vascular resistances: Preliminary results in the patients with sepsis

BACKGROUND

The use of the ultrasound (US) bedside examination is increasing for the detailed evaluation of the hemodynamic parameters, allowing the physicians to set the appropriate therapeutic strategies with greater precision.

OBJECTIVE

The aim of this study is to evaluate the hemodynamic parameters (the cardiac output or CO, the central venous pressure or CVP and the systemic vascular resistance or SVR) in the patients with sepsis, by using a bedside US approach.

METHODS

We consecutively enrolled n.82 patients of S.Andrea Hospital (n.47 with sepsis and n.35 without sepsis), examining the hemodynamic parameters by a bedside US evaluation.

RESULTS

The incidence of sepsis was more than 50% of cases. The patients with sepsis presented higher comorbidity and polypharmacy (p < 0.01, p < 0.001), with increased creatinine (p < 0.001) and consequent esteemed glomerular filtration rate (p < 0.01), C-reactive protein (p < 0.01), SOFA (Sepsis-related Organ Failure Assessment) score (p < 1.58×10-7) and reduced SVR (p < 0.05). The SOFA score was inversely related to the SVR (p < 0.05).

CONCLUSIONS

To our best knowledge, this is the first study with a bedside US protocol to measure SVR, beyond the abdominal and cardiac qualitative evaluation.

Intravenous fluid therapy in sepsis

Sepsis is the dysregulated immune response to severe infection that is common and lethal among critically ill patients. Fluid administration is a common treatment for hypotension and shock in early sepsis. Fluid therapy can also cause edema and organ dysfunction. Research on the best treatment strategies for sepsis has provided insights on the optimal timing, dose, and type of fluid to treat patients with sepsis. Initial research on early goal-directed therapy for sepsis included an initial bolus of 30 ml/kg of fluid, but more recent research has supported use of smaller volumes. After initial fluid resuscitation, minimizing additional fluid administration may be beneficial, but no single measure has been established as the best method to guide ongoing fluid management in sepsis. Dynamic measures of "fluid responsiveness" can predict which patients will experience an increase in cardiac output from a fluid bolus. Use of such a measure in clinical care remains limited by applicability to patient populations and uncertainty regarding the effect on clinical outcomes. Recent research informs the effect of fluid composition on outcomes for patients with sepsis. Current data support the use of balanced crystalloids, rather than saline, and the use of crystalloids, rather than semisynthetic colloids. The role for albumin administration in sepsis remains uncertain. Future research should focus on determining the optimal volume of fluid during sepsis resuscitation, the effectiveness of measures of "fluid responsiveness" in improving outcomes, the optimal composition of crystalloid solutions, the role of albumin, and the effects of "deresuscitation" after septic shock.

Relationship between pulse pressure variation and stroke volume variation with changes in cardiac index during hypotension in patients undergoing major spine surgeries in prone position - A prospective observational study

Background and Aims

Dynamic indices such as pulse pressure variation (PPV) and stroke volume variation (SVV) are better predictors of fluid responsiveness than static indices. There is a strong correlation between PPV and SVV in the prone position when assessed with the fluid challenge. However, this correlation has not been established during intraoperative hypotension. Our study aimed to assess the correlation between PPV and SVV during hypotension in the prone position and its relationship with cardiac index (CI).

Material and Methods

Thirty patients aged 18-70 years of ASA class I-III, undergoing spine procedures in the prone position were recruited for this prospective observational study. Hemodynamic variables such as heart rate (HR), mean arterial pressure (MAP), PPV, SVV, and CI were measured at baseline (after induction of anesthesia and positioning in the prone position). This set of variables were collected at the time of hypotension (T-before) and after correction (T-after) with either fluids or vasopressors. HR and MAP are presented as median with inter quartile range and compared by Mann-Whitney U test. Reliability was measured by intraclass correlation coefficients (ICC). Generalized estimating equations were performed to assess the change of CI with changes in PPV and SVV.

Results

A statistically significant linear relationship between PPV and SVV was observed. The ICC between change in PPV and SVV during hypotension was 0.9143, and after the intervention was 0.9091 (P < 0.001). Regression of changes in PPV and SVV on changes in CI depicted the reciprocal change in CI which was not statistically significant.

Conclusion

PPV is a reliable surrogate of SVV during intraoperative hypotension in the prone position.

Feasibility of Brachial Occlusion Technique for Beat-to-Beat Pulse Wave Analysis

Czech physiologist Penaz tried to overcome limitations of invasive pulse-contour methods (PCM) in clinical applications by a non-invasive method (finger mounted BP cuff) for continuous arterial waveform detection and beat-to-beat analysis. This discovery resulted in significant interest in human physiology and non-invasive examination of hemodynamic parameters, however has limitations because of the distal BP recording using a volume-clamp method. Thus, we propose a validation of beat-to-beat signal analysis acquired by novel a brachial occlusion-cuff (suprasystolic) principle and signal obtained from Finapres during a forced expiratory effort against an obstructed airway (Valsalva maneuver). Twelve healthy adult subjects [2 females, age = (27.2 ± 5.1) years] were in the upright siting position, breathe through the mouthpiece (simultaneously acquisition by brachial blood pressure monitor and Finapres) and at a defined time were asked to generate positive mouth pressure for 20 s (Valsalva). For the purpose of signal analysis, we proposed parameter a “Occlusion Cuff Index” (OCCI). The assumption about similarities between measured signals (suprasystolic brachial pulse waves amplitudes and Finapres’s MAP) were proved by averaged Pearson’s correlation coefficient (r- = 0.60, p < 0.001). The averaged Pearson’s correlation coefficient for the comparative analysis of OCCI between methods was r- = 0.88, p < 0.001. The average percent change of OCCI during maneuver: 8% increase, 19% decrease and percent change of max/min ratio is 35%. The investigation of brachial pulse waves measured by novel brachial blood pressure monitor shows positive correlation with Finapres and the parameter OCCI shows promise as an index, which could describe changes during beat-to-beat cardiac cycles.

Measurement of Cardiac Output Using an Ultrasonic Cardiac Output Monitor (USCOM) in Patients with Single-Ventricle Physiology

We evaluate the validity of cardiac index (CI) measurements utilizing the Ultrasonic Cardiac Output Monitor (USCOM), a non-invasive Doppler ultrasound device, by comparing measurements to cardiac catheterization-derived CI measurements in patients with single-ventricle physiology. USCOM measurements were repeated three times for each patient at the beginning of a cardiac catheterization procedure for twenty-six patients undergoing elective pre-Glenn or pre-Fontan catheterization. CI was measured by USCOM and was calculated from cardiac catheterization data using Fick's method. Bland-Altman analysis for CI showed bias of 0.95 L/min/m² with the 95% limits of agreement of - 1.85 and 3.75. Pearson's correlation coefficient was 0.89 (p < 0.001) indicating a strong positive relationship between USCOM and cardiac catheterization CI measurements. When excluding two patients with significant dilation of the neo-aortic valve (z-score >  + 5), the bias improved to 0.66 L/min/m² with the 95% limits of agreement of - 1.38 and 2.70. Percent error of limits of agreement was 34%. There was excellent intra-operator reproducibility of USCOM CI measurements with an intra-class coefficient of 0.96. We demonstrate the use of USCOM to measure CI in patients with single-ventricle physiology for the first time, showing acceptable agreement of the CI measurements between USCOM and cardiac catheterization with a high intra-operator reproducibility.

Fluid and Hemodynamics

Several components of an Enhanced Recovery After Surgery (ERAS) pathway act to improve and simplify perioperative fluid and hemodynamic therapy. Modern perioperative fluid management has shifted away from the liberal fluid therapy and toward more individualized approaches. Clinical evidence has also emphasized the importance of maintaining adequate mean arterial pressure and avoiding intraoperative hypotension. Goal-directed hemodynamic therapy (GDHT), or the use of cardiac output monitoring to guide fluid and vasopressor use, has been shown to reduce complications, but its role within ERAS pathways is likely best-suited to high-risk patients or those undergoing high-risk procedures. This article reviews the mechanisms by which ERAS pathways aid the provider in hemodynamic management, reviews trends, and evidence regarding fluid and hemodynamic therapy approaches, and provides guidance on the practical implementation of these concepts within ERAS pathways.

Comparison of Bioimpedance Versus Pulse Contour Analysis for Intraoperative Cardiac Index Monitoring in Patients Undergoing Kidney Transplantation

Background

Cardiac index (CI; cardiac output indexed to body surface area) is routinely measured during kidney transplant surgery. Bioimpedance cardiometry is a transthoracic impedance as the non-invasive alternative for hemodynamic monitoring, using semi-invasive uncalibrated pulse wave or contour (UPC) analysis.

Objectives

We performed a cross-sectional observational study on 50 kidney transplant patients to compare the CI measurement agreement, concordance rate, and trending ability between bioimpedance and UPC analysis.

Methods

For each patient, CI was measured by bioimpedance analysis (ICON^TM) and UPC analysis (EV1000^TM) devices at three time points: after induction, during incision, and at reperfusion. The device measurement accuracy was assessed by the bias value, limit of agreement (LoA), and percentage error (PE) using Bland-Altman analyses. Trending ability was assessed by angular bias and polar concordance through four-quadrant and polar plot analyses.

Results

From each time point and pooled measurement, the correlation coefficients were 0.267, 0.327, 0.321, and 0.348. Bland-Altman analyses showed mean bias values of 1.18, 1.06, 1.48, and 1.30, LoA of -1.35 to 3.72, -1.39 to 3.51, -1.07 to 4.04, and -1.17 to 3.78, and PE of 82.21, 78.50, 68.74, and 74.58%, respectively. Polar plot analyses revealed angular bias values of -10.37º, -15.01º, -18.68º, and -12.62º, with radial LoA of 89.79º, 85.86º, 83.38º, and 87.82º, respectively. The four-quadrant plot concordance rates were 70.77, 67.35, 65.90, and 69.79%. These analyses showed poor agreement, weak concordance, and low trending ability of bioimpedance cardiometry to UPC analysis.

Conclusions

Bioimpedance and UPC analysis for CI measurements were not interchangeable in patients undergoing kidney transplant surgery. Cardiac index monitoring using bioimpedance cardiometry during kidney transplantation should be interpreted cautiously because it showed poor reliability due to low accuracy, precision, and trending ability for CI measurement.

Development and Validation of an Arterial Pressure-Based Cardiac Output Algorithm Using a Convolutional Neural Network: Retrospective Study Based on Prospective Registry Data

Background

Arterial pressure-based cardiac output (APCO) is a less invasive method for estimating cardiac output without concerns about complications from the pulmonary artery catheter (PAC). However, inaccuracies of currently available APCO devices have been reported. Improvements to the algorithm by researchers are impossible, as only a subset of the algorithm has been released.

Objective

In this study, an open-source algorithm was developed and validated using a convolutional neural network and a transfer learning technique.

Methods

A retrospective study was performed using data from a prospective cohort registry of intraoperative bio-signal data from a university hospital. The convolutional neural network model was trained using the arterial pressure waveform as input and the stroke volume (SV) value as the output. The model parameters were pretrained using the SV values from a commercial APCO device (Vigileo or EV1000 with the FloTrac algorithm) and adjusted with a transfer learning technique using SV values from the PAC. The performance of the model was evaluated using absolute error for the PAC on the testing dataset from separate periods. Finally, we compared the performance of the deep learning model and the FloTrac with the SV values from the PAC.

Results

A total of 2057 surgical cases (1958 training and 99 testing cases) were used in the registry. In the deep learning model, the absolute errors of SV were 14.5 (SD 13.4) mL (10.2 [SD 8.4] mL in cardiac surgery and 17.4 [SD 15.3] mL in liver transplantation). Compared with FloTrac, the absolute errors of the deep learning model were significantly smaller (16.5 [SD 15.4] and 18.3 [SD 15.1], P<.001).

Conclusions

The deep learning–based APCO algorithm showed better performance than the commercial APCO device. Further improvement of the algorithm developed in this study may be helpful for estimating cardiac output accurately in clinical practice and optimizing high-risk patient care.

Prognostic value of baseline carotid blood flow in critically ill children with septic shock

Background and aim

Hemodynamic monitoring and cardiac output (CO) assessment in the ICU have been trending toward less invasive methods. Carotid blood flow (CBF) was suggested as a candidate for CO assessment. The present study aimed to test the value of carotid artery ultrasound analysis in prediction of mortality in pediatric patients with septic shock.

Methodology/Principal finding

Forty children with septic shock were included in the study. Upon admission, patients were subjected to careful history taking and thorough clinical examination. The consciousness level was assessed by the Glasgow Coma Scale (GCS). Laboratory assessment included complete blood count, C-reactive protein, arterial blood gases, serum electrolytes, and liver and kidney function tests. Electrical cardiometry was used to evaluate hemodynamic parameters. Patients were also subjected to transthoracic 2-D echocardiography. CBF was evaluated using GE Vivid S5 ultrasound device through dedicated software. At the end of study, 14 patients (35.0%) died. It was found that survivors had significantly higher CBF when compared non-survivors [median (IQR): 166.0 (150.0–187.3) versus 141.0 (112.8–174.3), p = 0.033]. In addition, it was noted that survivors had longer ICU stay when compared with non-survivors [16.5 (9.8–31.5) versus 6.5 (3.0–19.5) days, p = 0.005]. ROC curve analysis showed that CBF could significantly distinguish survivors from non-survivors [AUC (95% CI): 0.3 (0.11–0.48), p = 0.035] (Fig 2). Univariate logistic regression analysis identified type of shock [OR (95% CI): 28.1 (4.9–162.4), p<0.001], CI [OR (95% CI): 0.6 (0.43–0.84), p = 0.003] and CBF [OR (95% CI): 0.98 (0.96–0.99), p = 0.031]. However, in multivariate analysis, only type of shock significantly predicted mortality.

Conclusions

CBF assessment may be a useful prognostic marker in children with septic shock.

Updates in Hemodynamic Monitoring: A Review for Pharmacists

Vital signs are regularly monitored in hospitalized patients. In the intensive care unit (ICU), traditional non-invasive blood pressure monitoring and telemetry may not provide enough information to determine the etiology of hemodynamic instability or guide intervention. Arterial catheters remain the gold-standard for continuous blood pressure monitoring and are commonly used in ICU patients. Pulmonary artery catheters and central venous catheters are beneficial in select patient populations and provide more advanced and specific information about a patient's hemodynamics. However, neither are benign and can increase risk of complications such as infection, arrhythmias, pneumothorax and vascular or valvular damage. In the past 10 years, the development of reliable non-invasive (NICOM), or minimally-invasive (MICOM), cardiac output monitoring devices has accelerated. The MICOM devices require an arterial catheter to obtain hemodynamic values, whereas NICOM devices do not require any arterial or venous access. These devices have emerged to be particularly useful in evaluating and managing patients with suspected mixed shock. As these devices become more prevalent, it is imperative that clinical pharmacists become familiar with interpreting this data as it may have a substantial impact on medication selection and optimization. This review will discuss the basics of NICOM and MICOM devices, limitations with these methods of monitoring, and clinical application for pharmacists.

Excess pressure as an analogue of blood flow velocity

INTRODUCTION

Derivation of blood flow velocity from a blood pressure waveform is a novel technique, which could have potential clinical importance. Excess pressure, calculated from the blood pressure waveform via the reservoir-excess pressure model, is purported to be an analogue of blood flow velocity but this has never been examined in detail, which was the aim of this study.

METHODS

Intra-arterial blood pressure was measured sequentially at the brachial and radial arteries via fluid-filled catheter simultaneously with blood flow velocity waveforms recorded via Doppler ultrasound on the contralateral arm (n = 98, aged 61 ± 10 years, 72% men). Excess pressure was derived from intra-arterial blood pressure waveforms using pressure-only reservoir-excess pressure analysis.

RESULTS

Brachial and radial blood flow velocity waveform morphology were closely approximated by excess pressure derived from their respective sites of measurement (median cross-correlation coefficient r = 0.96 and r = 0.95 for brachial and radial comparisons, respectively). In frequency analyses, coherence between blood flow velocity and excess pressure was similar for brachial and radial artery comparisons (brachial and radial median coherence = 0.93 and 0.92, respectively). Brachial and radial blood flow velocity pulse heights were correlated with their respective excess pressure pulse heights (r = 0.53, P < 0.001 and r = 0.43, P < 0.001, respectively).

CONCLUSION

Excess pressure is an analogue of blood flow velocity, thus affording the opportunity to derive potentially important information related to arterial blood flow using only the blood pressure waveform.

Cardiac Output Evaluation on Septic Shock Patients: Comparison between Calibrated and Uncalibrated Devices during Vasopressor Therapy

There are no reliable, non-invasive methods to accurately measure cardiac output (CO) in septic patients. MostCare (Vytech Health™, Vygon, Padova, Italy), is a beat-to-beat, self calibrated method for CO measurement based on continuous analysis of reflected arterial pressure waveforms. We enrolled 40 patients that were suffering from septic shock and requiring norepinephrine infusion to target blood pressure in order to to evaluate the level of agreement between a calibrated transpulmonary thermodilution device (PiCCO System, Pulsion Medical Systems, Feldkirchen, Germany) and the MostCare system in detecting and tracking changes in CO measurements related to norepinephrine reduction in septic shock patients,. PiCCO was connected to a 5 Fr femoral artery catheter and to a central venous catheter. System calibration was performed with 15 mL of cold saline injection over about 3 s. The MostCare device was connected to the artery catheter to analyze the arterial waveform. Before reducing norepinephrine infusion, the PiCCO system was calibrated, the MostCare waveform was optimized, and the values of the complete hemodynamic profile were recorded (T1). Norepinephrine infusion was then reduced by 0.03 mcg/Kg/min. After 30 min, a new calibration of PiCCO system and a new record on both monitors were performed (T2). Static measurements agreements were assessed using the Bland-Altman test, while trending ability was investigated using polar plot analysis. If volume expansion occurred, then related data were separately analyzed. At T1 mean the CO was 5.38 (SD 0.60) L/min, the mean difference was 0.176 L/min, the limits of agreement (LoA) was +1.39 and -1.04 L/min, and the percentage error (PE) was 22.6%; at T2 the mean CO was 5.44 (SD 0.73) L/min, the mean difference was 0.053 L/min, the LoA was +1.51 and -1.40, and the PE was 27%. After considering the volume expansion between T1 and T2, the mean CO at T1 was 5.39 L/min (SD 0.47), the LoA was +1.09 and -0.78 L/min, and the percentage error (PE) was 17%; at T2 the mean CO was 5.35 L/min (SD 0.81), the LoA was +1.73 and -1.52 L/min, and the PE was 30%. The polar plot diagram seems to confirm the trending ability of MostCare system versus the reference method. In septic patients, when the arterial waveform is accurate, MostCare and PiCCO transpulmonary thermodilution exhibit good agreement even after the reduction of norepinephrine and changes in vascular tone or volume expansion. MostCare could be a rapid to set, reliable, and useful tool to monitor hemodynamic variations in septic patients in emergency contexts where thermodilution methods or other advanced systems are not easily available.

The influence of cardiac output on propofol and fentanyl pharmacokinetics and pharmacodynamics in patients undergoing abdominal aortic surgery

Cardiac output (CO) is expected to affect elimination and distribution of highly extracted and perfusion rate-limited drugs. This work was undertaken to quantify the effect of CO measured by the pulse pressure method on pharmacokinetics and pharmacodynamics of propofol and fentanyl administrated during total intravenous anesthesia (TIVA). The data were obtained from 22 ASA III patients undergoing abdominal aortic surgery. Propofol was administered via target-controlled infusion system (Diprifusor) and fentanyl was administered at a dose of 2-3 µg/kg each time analgesia appeared to be inadequate. Hemodynamic measurements as well as bispectral index were monitored and recorded throughout the surgery. Data analysis was performed by using a non-linear mixed-effect population modeling (NONMEM 7.4 software). Three compartment models that incorporated blood flows as parameters were used to describe propofol and fentanyl pharmacokinetics. The delay of the anesthetic effect, with respect to plasma concentrations, was described using a biophase (effect) compartment. The bispectral index was linked to the propofol and fentanyl effect site concentrations through a synergistic Emax model. An empirical linear model was used to describe CO changes observed during the surgery. Cardiac output was identified as an important predictor of propofol and fentanyl pharmacokinetics. Consequently, it affected the depth of anesthesia and the recovery time after propofol-fentanyl TIVA infusion cessation. The model predicted (not observed) CO values correlated best with measured responses. Patients' age was identified as a covariate affecting the rate of CO changes during the anesthesia leading to age-related difference in individual patient's responses to both drugs.

Implementation and Calibration of a Deep Neural Network to Predict Parameters of Left Ventricular Systolic Function Based on Pulmonary and Systemic Arterial Pressure Signals

The evaluation of cardiac contractility by the assessment of the ventricular systolic elastance function is clinically challenging and cannot be easily obtained at the bedside. In this work, we present a framework characterizing left ventricular systolic function from clinically readily available data, including systemic and pulmonary arterial pressure signals. We implemented and calibrated a deep neural network (DNN) consisting of a multi-layer perceptron with 4 fully connected hidden layers and with 16 neurons per layer, which was trained with data obtained from a lumped model of the cardiovascular system modeling different levels of cardiac function. The lumped model included a function of circulatory autoregulation from carotid baroreceptors in pulsatile conditions. Inputs for the DNN were systemic and pulmonary arterial pressure curves. Outputs from the DNN were parameters of the lumped model characterizing left ventricular systolic function, especially end-systolic elastance. The DNN adequately performed and accurately recovered the relevant hemodynamic parameters with a mean relative error of less than 2%. Therefore, our framework can easily provide complex physiological parameters of cardiac contractility, which could lead to the development of invaluable tools for the clinical evaluation of patients with severe cardiac dysfunction.

Cardiac eigen imaging: a novel method to isolate cardiac activity in thoracic electrical impedance tomography

OBJECTIVE

As the global burden of cardiovascular disease increases, proactive cardiovascular healthcare by means of accurate, precise, continuous, and non-invasive monitoring is becoming crucial. However, no current device is able to provide cardiac hemodynamic monitoring with the aforementioned criterion. Electrical impedance tomography (EIT) is an inexpensive, non-invasive imaging modality that can provide real-time images of internal conductivity distributions that describe physiological activity. This work explores and compares a standard approach of regular cardiac gated averaging (RCGA) and a newly developed method, cardiac eigen-imaging (CEI), based on the singular value decomposition (SVD) to isolate cardiac activity in thoracic EIT.

APPROACH

EIT and heart-rate (HR) data were collected from 20 heart-failure patients preceding echocardiography. Features from RCGA and CEI images were correlated with stroke volume (SV) from echocardiography and image reconstruction parameters were optimized using leave-one-out (LOO) cross-validation.

MAIN RESULTS

CEI per-pixel-based features achieved a Pearson correlation coefficient of 0.80 with SV relative to 0.72 with RCGA. CEI had 33 high-correlating pixels while RCGA had 8. High-correlating pixels tend to concentrate in the right-ventricle (RV) when referenced to a general chest model.

SIGNIFICANCE

While both RCGA and CEI images had high-correlating pixels, CEI had higher correlations, a larger number of high-correlating pixels, and unlike RCGA is not dependent on the quality of the HR data collected. The observed performance of the CEI approach represents a promising step forward for EIT-based cardiac monitoring in either clinical or ambulatory settings.

Semiquantification of Systemic Venous Admixture During Venovenous Extracorporeal Oxygenation Via Bicaval Double-Lumen Cannula in Critically Ill Patients

Venovenous extracorporeal membrane oxygenation (VV-ECMO) is increasingly utilized in acute reversible cases of severe respiratory failure and as a bridge to lung transplantation. Venovenous extracorporeal membrane oxygenation using a bicaval double-lumen cannula (BCDLC) has several advantages over the traditional ECMO configuration; however, it also presents with several unique challenges. The assessment and quantification of venous admixture is difficult due to the specific position of BCDLC within the circulatory system. We describe the nature of the double-lumen bicaval venovenous ECMO cannula and relevant specific issues associated with monitoring complex details of oxygenation within different parts of circulation, including existing barriers for quantification of recirculation and venous admix. New conceptual approach to the quantification of venous admix is described. Right side echocardiographic contrast, when sequentially injected in separate superior vena cava (SVC) and inferior vena cava (IVC) venous basins, bypasses drainage ports of the catheter in double-lumen bicaval VV-ECMO configuration together with deoxygenated returning from the periphery venous blood. It was easily detectable entering right heart chambers by two- and three-dimensional echocardiography. Amount of bubbles from the agitated fluid contrast within right atrium indicates relative amount of venous admixture in relation to the returning from the oxygenator blood which is bubble free.

The cardiac output optimisation following liver transplant (COLT) trial: a feasibility randomised controlled trial

BACKGROUND

Perioperative goal directed fluid therapy (GDFT) has been shown to reduce postoperative complications following major surgery; this intervention has not been formally evaluated in the setting of liver transplantation.

METHODS

We conducted a prospective trial of GDFT following liver transplantation randomising patients with liver cirrhosis to either 12 h of GDFT using non-invasive cardiac output monitoring or standard care (SC). The primary outcome was feasibility. Secondary outcomes included survival, postoperative complications (Clavien-Dindo), quality of life (by EQ-5D-5L) and resource use. Trial specific follow up occurred at 90 and 180 days after surgery.

RESULTS

The study was feasible. Of 224 eligible patients, 122 were approached, 114 consented to participate and 60 were enrolled into the trial. The mean (SD) volume of IV crystalloid administered to the GDFT group during the 12-h study period was 3968 (2073) ml for the GDFT group and 2510 (1026) ml for the SC group. As regards secondary outcomes there was no difference in survival or overall complication rates. There was no significant difference in quality of life scores and resource use between the groups.

CONCLUSION

A randomised study of GDFT following liver transplantation is feasible. A post-trial stakeholder meeting supported proceeding with a full multi-centre trial.

Dilated Cardiomyopathy and Prone Position: An Anesthetic Challenge

The anesthetic management of a patient with dilated cardiomyopathy (DCM) for noncardiac surgery is challenging due to associated congestive heart failure, malignant dysrhythmias, sudden cardiac arrest, implanted rhythm devices, and thromboembolism. We report successful conduct of a case of DCM on cardiac resynchronization device with Cauda equina syndrome (CES) under general anesthesia in prone position. The anesthetic concerns specific to the pathophysiology of DCM are also discussed.

Comparing the Mutual Interchangeability of ECOM, FloTrac/Vigileo, 3D-TEE, and ITD-PAC Cardiac Output Measuring Systems in Coronary Artery Bypass Grafting

OBJECTIVE

The aim of this study was to compare the mutual interchangeability of 4 cardiac output measuring devices by comparing their accuracy, precision, and trending ability.

DESIGN

A single-center prospective observational study.

DESIGN

Nonuniversity teaching hospital, single center.

PARTICIPANTS

Forty-four consecutive patients scheduled for elective, nonemergent coronary artery bypass grafting (CABG).

INTERVENTIONS

The cardiac output was measured for each participant using 4 methods: intermittent thermodilution via pulmonary artery catheter (ITD-PAC), Endotracheal Cardiac Output Monitor (ECOM), FloTrac/Vigileo System (FLOTRAC), and 3-dimensional transesophageal echocardiography (3D-TEE).

MEASUREMENTS AND MAIN RESULTS

Measurements were performed simultaneously at 5 time points: presternotomy, poststernotomy, before cardiopulmonary bypass, after cardiopulmonary bypass, and after sternal closure. A series of statistical and comparison analyses including ANOVA, Pearson correlation, Bland-Altman plots, quadrant plots, and polar plots were performed, and inherent precision for each method and percent errors for mutual interchangeability were calculated. For the 6 two-by-two comparisons of the methods, the Pearson correlation coefficients (r), the percentage errors (% error), and concordance ratios (CR) were as follows: ECOM_versus_ITD-PAC (r = 0.611, % error = 53%, CR = 75%); FLOTRAC_versus_ITD-PAC (r = 0.676, % error = 49%, CR = 77%); 3D-TEE versus ITD-PAC (r = 0.538, % error = 64%, CR = 67%); FLOTRAC_versus_ECOM (r = 0.627, % error = 51%, CR = 75%); 3D-TEE_versus ECOM (r = 0.423, % error = 70%, CR = 60%), and 3D-TEE_versus_FLOTRAC (r = 0.602, % error = 59%, CR = 61%).

CONCLUSIONS

Based on the recommended statistical measures of interchangeability, ECOM, FLOTRAC, and 3D-TEE are not interchangeable with each other or to the reference standard invasive ITD-PAC method in patients undergoing nonemergent cardiac bypass surgery. Despite the negative result in this study and the majority of previous studies, these less-invasive methods of CO have continued to be used in the hemodynamic management of patients. Each device has its own distinct technical features and inherent limitations; it is clear that no single device can be used universally for all patients. Therefore, different methods or devices should be chosen based on individual patient conditions, including the degree of invasiveness, measurement performance, and the ability to provide real-time, continuous CO readings.

Accuracy and precision of cardiac output estimation by an automated, brachial cuff-based oscillometric device in patients with shock

Non-invasive monitoring of cardiac output is a technological and clinical challenge, especially for critically ill, surgically operated, or intensive care unit patients. A brachial cuff-based, automated, oscillometric device used for blood pressure and arterial stiffness ambulatory monitoring (Mobil-O-Graph) provides a non-invasive estimation of cardiac output values simultaneously with regular blood pressure measurement. The aim of the study was to evaluate the feasibility of this apparatus to estimate cardiac output in intensive care unit patients and to compare the non-invasive estimated cardiac output values with the respective gold standard method of thermodilution during pulmonary artery catheterization. Repeated sequential measurements of cardiac output were performed, in random order, by thermodilution (reference) and Mobil-O-Graph (test), in 24 patients hospitalized at intensive care unit. Reproducibility and accuracy of the test device were evaluated by Bland–Altman analysis, intraclass correlation coefficient, and percentage error. Mobil-O-Graph underestimated significantly the cardiac output by −1.12 ± 1.38 L/min ( p < 0.01) compared to thermodilution. However, intraclass correlation coefficient was >0.7 indicating a fair agreement between the test and the reference methods, while percentage error was approximately 39% which is considered to be within the acceptable limits. Cardiac output measurements were reproducible by both Mobil-O-Graph (intraclass correlation coefficient = 0.73 and percentage error = 27.9%) and thermodilution (intraclass correlation coefficient = 0.91 and percentage error = 26.7%). We showed for the first time that cardiac output estimation in intensive care unit patients using a non-invasive, automated, oscillometric, cuff-based apparatus is reproducible (by analyzing two repeated cardiac output measurements), exhibiting similar precision to thermodilution. However, the accuracy of Mobil-O-Graph (error compared to thermodilution) could be considered fairly acceptable. Future studies remain to further examine the reliability of this technology in monitoring cardiac output or stroke volume acute changes which is a more clinically relevant objective.

Effect of preoperative fluid therapy on hemodynamic stability during anesthesia induction, a randomized study

BACKGROUND

Preserving perfusion pressure during anesthesia induction is crucial. Standardized anesthesia methods, alert fluid therapy and vasoactive drugs may help maintain adequate hemodynamic conditions throughout the induction procedure. In this randomized study, we hypothesized that a pre-operative volume bolus based on lean body weight would decrease the incidence of significant blood pressure drops (BPD) after induction with target-controlled infusion (TCI) or rapid sequence induction (RSI).

METHODS

Eighty individuals scheduled for non-cardiac surgery were randomized to either a pre-operative colloid fluid bolus of 6 ml kg^-1 lean body weight or no bolus, and then anesthetized by means of TCI or RSI. The main outcome measure was blood pressure drops below the mean arterial pressure 65 mm Hg during the first 20 minutes after anesthesia induction. ClinicalTrials.com Identifier: NCT03394833.

RESULTS

Pre-operative fluid therapy decreased the incidence of BPDs fivefold, from 23 of 40 (57.5%) individuals without fluids to 5 of 40 (12.5%) with fluid management, P < .001. The mean BPD was greater in the groups without pre-operative fluids compared to the groups with fluid management; 53 ± 18 mm Hg vs 43 ± 14 mm Hg, P = .007. The overall mean volume of pre-operative fluid bolus infused was 387 ± 52 ml. There was no difference in hemodynamic stability between TCI and RSI. No correlation was shown between incidence of BPDs and increasing age, medication, hypertension, diabetes, renal failure, or low physical capacity.

CONCLUSIONS

Pre-operative fluid bolus decreased the incidence of significant blood pressure drops during TCI and RSI induction of general anesthesia.

Noise-robust bioimpedance approach for cardiac output measurement

OBJECTIVE

Congestive heart failure is a problem affecting millions of Americans. A continuous, non-invasive, telemonitoring device that can accurately monitor cardiac metrics could greatly help this population, reducing unnecessary hospitalizations and cost.

APPROACH

Machine learning (ML) algorithms trained on electrical-impedance tomography (EIT) data are presented for portable cardiac monitoring. The approach was validated on a simulated thorax and a measured tank experiment. A highly detailed 4D chest model (finite element method mesh and conductivity profiles) was developed utilizing the 4D XCAT phantom to provide realistic data. The ML algorithms were trained using databases that assumed the presence of poorly contacting electrodes without any assumptions of knowing which electrodes would be bad in the experiment. The trained ML algorithms were compared to EIT evaluated with and without removing bad electrodes.

MAIN RESULTS

A regression support vector machine and a deep neural network (DNN) were found to be the most accurate and robust to poorly contacting electrodes while not needing to know which electrodes were in poor contact in the simulated and measured experiments, respectively.

SIGNIFICANCE

Although the ML algorithms are not always better than EIT (with bad electrodes removed), the comparable results without needing a priori knowledge of which electrodes are bad is seen as a very promising feature. An evaluation of computational costs showed that the DNN required comparable computational power to the other methods while requiring less memory, which could make the DNNs an attractive algorithm for a low-power, portable system. This work represents an important validation of the method using measured data, and model development, which is needed to apply this method on real clinical data. Additionally, the developed 4D simulated thorax model could be an important tool within the EIT community.

Haemodynamic changes during prone positioning in anaesthetised chronic cervical myelopathy patients

Background and Aims:

Anaesthetised patients, when positioned prone, experience hypotension and reduction in cardiac output. Associated autonomic dysfunction in cervical myelopathy patients predisposes them to haemodynamic changes. The combined effect of prone positioning and autonomic dysfunction in anaesthetised patients remains unknown.

Methods:

Thirty adult chronic cervical myelopathy patients, aged 18-65 years with Nurick grade ≥2 were recruited in this prospective observational study. Heart rate, mean blood pressure, cardiac output, stroke volume, total peripheral resistance and stroke volume variation were measured using NICOM^® monitor. Data were collected in supine before anaesthetic induction (baseline), 2 minutes after induction, 2 minutes after intubation, before and after prone positioning and every 5 minutes thereafter until skin incision. Repeated measures analysis of variance (ANOVA) was used to analyse the haemodynamic parameters across the time points. Bivariate Spearman's correlation was used to find factors associated with blood pressure changes. A P value <0.05 was kept significant.

Results:

Cardiac output during the entire study period remained stable (P = 0.186). Sixty percent of the patients experienced hypotension. At 15 and 20 minutes after prone positioning, mean blood pressure decreased (P = 0.001), stroke volume increased (P = 0.001), and heart rate and total peripheral resistance decreased (P < 0.001, P = 0.001, respectively). These changes were significant when compared to pre-prone position values. Number of levels of spinal cord compression positively correlated with the incidence of hypotension.

Conclusion:

Cervical myelopathy patients experienced hypotension with preserved cardiac output in prone position due to a reduction in total peripheral resistance. Hypotension correlated with the number of levels of spinal cord compression.

Impact of postoperative intravenous fluid administration on complications following elective hepato-pancreato-biliary surgery

BACKGROUND

The impact of perioperative intravenous fluid administration on surgical outcomes has been documented in literature, but not specifically studied in the context of hepato-pancreato-biliary (HPB) surgery. This study aimed to investigate the impact of postoperative intravenous fluid administration on intensive care unit (ICU), in this subgroup of patients.

METHODS

A single-center retrospective cohort of 241 HPB patients was assessed, focusing on intravenous fluid administration in ICU, during the first 24 h. Intravenous fluid variables were compared to hospital stay and postoperative complications. Data were assessed using Spearman's correlation test for bivariate correlations and logistic regression for multivariate analysis.

RESULTS

The median volume of intravenous fluid administered in the first 24 h postoperatively was 4380 mL, of which 2200 mL was crystalloid, 1500 mL colloid and 680 mL "other" fluid. Patients with one or more complications had a higher median total intravenous fluid input (4790 vs. 4300 mL), higher colloid volume (2000 vs. 1500 mL), lower urine output (1595 vs. 1900 mL) and greater overall fluid balance (+3040 vs.+2553 mL) than those without complications. There were correlations between total intravenous fluid volume administered (r = 0.278, P < 0.001), intravenous colloid input (r = 0.278, P < 0.001), urine output (r = -0.295, P < 0.001), positive fluid balance (r = 0.344, P < 0.001) and length of hospital stay. Logistic regression model was constructed to predict the occurrence of one or more complications; total intravenous fluid volume and overall fluid balance were both independent significant predictors (OR = 2.463, P = 0.007; OR = 1.001, P = 0.011; respectively).

CONCLUSIONS

Administration of high volumes of intravenous fluids in the first 24 hours post-HPB surgery, along with higher positive fluid balance is associated with a higher rate of complications and longer hospital stay. Moreover, lower urine output is associated with longer hospital stay. Whether these are the cause of complications or the result of them remains unclear.

Assessment of cardiac function in infants with transposition of the great arteries after surgery: comparison of two methods

BACKGROUND

Assessment of cardiac function is crucial in pediatric patients undergoing cardiovascular surgery, monitoring cardiac output and changing hemodynamic conditions during surgery accordingly is important to improve post-surgical outcome. We aimed to measure cardiac index (CI) and maximal rate of the increase of left ventricular pressure dp/dt(max) with the pressure recording analytic method (PRAM, MostCare^®) and compared it with transthoracic echocardiographic cardiac index estimation in infants with transposition of the great arteries (TGA) undergoing surgical correction.

METHODS

We enrolled 74 infants with TGA consecutively into this study. CI and dp/dt(max) were measured with PRAM and echocardiography at 0, 4, 8, 12, 24 and 48 h postoperatively. Blood brain natriuretic peptide (BNP) and blood lactate (Lac) were measured at baseline and after operation.

RESULTS

The median age at surgery was 13 days (range 1-25 days) with an average weight of 3.24 kg (range 2.31-4.17 kg). CI estimated by PRAM was 1.11 ± 0.12 L/min/m² (range 0.69-1.36) and by Doppler echocardiography was 1.13 ± 0.13 L/min/m² (range 0.76-1.40). dp/dt(max) estimated by PRAM was 1.31 ± 0.03 mmHg/s (range 1.23-1.43) and by Doppler echocardiography was 1.31 ± 0.04 L/min/m² (range 1.25-1.47). CI (r = 0.817, P < 0.001) and dp/dt(max) (r = 0.794, P < 0.001) measured by two methods were highly correlated with a linear relation. Blood BNP and lactate increased to the highest level at 8-12 h post-operatively.

CONCLUSIONS

In the early post-operative period, PRAM provides reliable estimates of cardiac index and dp/dt(max) value compared with echocardiographic measurements. PRAM through mostcare^® is a reliable continuous monitoring method for peri-operative management in children with congenital heart disease.

Fluid Management in Sepsis

Among critically ill adults, sepsis remains both common and lethal. In addition to antibiotics and source control, fluid resuscitation is a fundamental sepsis therapy. The physiology of fluid resuscitation for sepsis, however, is complex. A landmark trial found early goal-directed sepsis resuscitation reduced mortality, but 3 recent multicenter trials did not confirm this benefit. Multiple trials in resource-limited settings have found increased mortality with early fluid bolus administration in sepsis, and the optimal approach to early sepsis resuscitation across settings remains unknown. After initial resuscitation, excessive fluid administration may contribute to edema and organ dysfunction. Using dynamic variables such as passive leg raise testing can predict a patient's hemodynamic response to fluid administration better than static variables such as central venous pressure. Whether using measures of "fluid responsiveness" to guide fluid administration improves patient outcomes, however, remains unknown. New evidence suggests improved patient outcomes with the use of balanced crystalloids compared to saline in sepsis. Albumin may be beneficial in septic shock, but other colloids such as starches, dextrans, and gelatins appear to increase the risk of death and acute kidney injury. For the clinician caring for patients with sepsis today, the initial administration of 20 mL/kg of intravenous balanced crystalloid, followed by consideration of the risks and benefits of subsequent fluid administration represents a reasonable approach. Additional research is urgently needed to define the optimal dose, rate, and composition of intravenous fluid during the management of patients with sepsis and septic shock.

Utility of central venous pressure measurement in renal transplantation: Is it evidence based?

Adequate intravenous fluid therapy is essential in renal transplant recipients to ensure a good allograft perfusion. Central venous pressure (CVP) has been considered the cornerstone to guide the fluid therapy for decades; it was the only available simple tool worldwide. However, the revolutionary advances in assessing the dynamic preload variables together with the availability of new equipment to precisely measure the effect of intravenous fluids on the cardiac output had created a question mark on the future role of CVP. Despite the critical role of fluid therapy in the field of transplantation. There are only a few clinical studies that compared the CVP guided fluid therapy with the other modern techniques and their relation to the outcome in renal transplantation. Our work sheds some light on the available published data in renal transplantation, together with data from other disciplines evaluating the utility of central venous pressure measurement. Although lager well-designed studies are still required to consolidate the role of new techniques in the field of renal transplantation, we can confidently declare that the new techniques have the advantages of providing more accurate haemodynamic assessment, which results in a better patient outcome.

Comparison of three non-invasive hemodynamic monitoring methods in critically ill children

Introduction

Hemodynamic parameters measurements were widely conducted using pulmonary artery catheter (PAC) with thermodilution as a reference standard. Due to its technical difficulties in children, transthoracic echocardiography (TTE) has been widely employed instead. Nonetheless, TTE requires expertise and is time-consuming. Noninvasive cardiac output monitoring such as ultrasonic cardiac output monitor (USCOM) and electrical velocimetry (EV) can be performed rapidly with less expertise requirement. Presently, there are inconsistent evidences, variable precision, and reproducibility of EV, USCOM and TTE measurements. Our objective was to compare USCOM, EV and TTE in hemodynamic measurements in critically ill children.

Materials and methods

This was a single center, prospective observational study in critically ill children. Children with congenital heart diseases and unstable hemodynamics were excluded. Simultaneous measurements of hemodynamic parameters were conducted using USCOM, EV, and TTE. Inter-rater reliability was determined. Bland-Altman plots were used to analyse agreement of assessed parameters.

Results

Analysis was performed in 121 patients with mean age of 4.9 years old and 56.2% of male population. Interrater reliability showed acceptable agreement in all measured parameters (stroke volume (SV), cardiac output (CO), velocity time integral (VTI), inotropy (INO), flow time corrected (FTC), aortic valve diameter (AV), systemic vascular resistance (SVR), and stroke volume variation (SVV); (Cronbach’s alpha 0.76–0.98). Percentages of error in all parameters were acceptable by Bland-Altman analysis (9.2–28.8%) except SVR (30.8%) and SVV (257.1%).

Conclusion

Three noninvasive methods might be used interchangeably in pediatric critical care settings with stable hemodynamics. Interpretation of SVV and SVR measurements must be done with prudence.

Clinical examination for diagnosing circulatory shock

PURPOSE OF REVIEW

In the acute setting of circulatory shock, physicians largely depend on clinical examination and basic laboratory values. The daily use of clinical examination for diagnostic purposes contrasts sharp with the limited number of studies. We aim to provide an overview of the diagnostic accuracy of clinical examination in estimating circulatory shock reflected by an inadequate cardiac output (CO).

RECENT FINDINGS

Recent studies showed poor correlations between CO and mottling, capillary refill time or central-to-peripheral temperature gradients in univariable analyses. The accuracy of physicians to perform an educated guess of CO based on clinical examination lies around 50% and the accuracy for recognizing a low CO is similar. Studies that used predefined clinical profiles composed of several clinical examination signs show more reliable estimations of CO with accuracies ranging from 81 up to 100%.

SUMMARY

Single variables obtained by clinical examination should not be used when estimating CO. Physician's educated guesses of CO based on unstructured clinical examination are like the 'flip of a coin'. Structured clinical examination based on combined clinical signs shows the best accuracy. Future studies should focus on using a combination of signs in an unselected population, eventually to educate physicians in estimating CO by using predefined clinical profiles.

Prediction of fluid responsiveness in mechanically ventilated cardiac surgical patients: the performance of seven different functional hemodynamic parameters

Background

Functional hemodynamic parameters such as stroke volume and pulse pressure variation (SVV and PPV) have been shown to be reliable predictors of fluid responsiveness in mechanically ventilated patients. Today, different minimally- and non-invasive hemodynamic monitoring systems measure functional hemodynamic parameters. Although some of these parameters are described by the same name, they differ in their measurement technique and thus may provide different results. We aimed to test the performance of seven functional hemodynamic parameters simultaneously in the same clinical setting.

Methods

Hemodynamic measurements were done in 30 cardiac surgery patients that were mechanically ventilated. Before and after a standardized intravenous fluid bolus, hemodynamics were measured by the following monitoring systems: PiCCOplus (SVV_PiCCO, PPV_PiCCO), LiDCO_rapid (SVV_LiDCO, PPV_LiDCO), FloTrac (SVV_FloTrac), Philips Intellivue (PPV_Philips) and Masimo pulse oximeter (pleth variability index, PVI). Prediction of fluid responsiveness was tested by calculation of receiver operating characteristic (ROC) curves including a gray zone approach and compared using Fisher’s Z-Test.

Results

Fluid administration resulted in an increase in cardiac output, while all functional hemodynamic parameters decreased. A wide range of areas under the ROC-curve (AUC’s) was observed: AUC-SVV_PiCCO = 0.91, AUC-PPV_PiCCO = 0.88, AUC-SVV_LiDCO = 0.78, AUC-PPV_LiDCO = 0.89, AUC-SVV_FloTrac = 0.87, AUC-PPV_Philips = 0.92 and AUC-PVI = 0.68. Optimal threshold values for prediction of fluid responsiveness ranged between 9.5 and 17.5%. Lowest threshold values were observed for SVV_LiDCO, highest for PVI.

Conclusion

All functional hemodynamic parameters tested except for PVI showed that their use allows a reliable identification of potential fluid responders. PVI however, may not be suitable after cardiac surgery to predict fluid responsiveness.

Trial registration

NCT02571465, registered on October 7th, 2015 (retrospectively registered).

Non-invasive measurement of cardiac output in children with repaired coarctation of the aorta using electrical cardiometry compared to transthoracic Doppler echocardiography

OBJECTIVE

To evaluate the equivalence of the ICON^® electrical cardiometry (EC) haemodynamic monitor to measure cardiac output (CO) relative to transthoracic Doppler echocardiography (TTE) in paediatric patients with repaired coarctation of the aorta (CoA).

APPROACH

A group of n  =  28 CoA patients and n  =  27 matched controls were enrolled. EC and TTE were performed synchronously on each participant and CO measurements compared using linear regression and Bland-Altman analysis. The CoA group was further subdivided into two groups, with n  =  10 and without n  =  18 increased left ventricular outflow tract velocity (iLVOTv) for comparison.

MAIN RESULTS

CO measurements from EC and TTE in controls showed a strong correlation (R  =  0.80, p  <  0.001) and an acceptable percentage error (PE) of 28.1%. However, combining CoA and control groups revealed a moderate correlation (R  =  0.57, p  <  0.001) and a poor PE (44.2%). We suspected that the CO in a subset of CoA participants with iLVOTv was overestimated by TTE. Excluding the iLVOTv CoA participants improved the correlation (R  =  0.77, p  <  0.001) and resulted in an acceptable PE of 31.2%.

SIGNIFICANCE

CO measurements in paediatric CoA patients in the absence of iLVOTv are clinically equivalent between EC and TTE. The presence of iLVOTv may impact the accuracy of CO measurement by TTE, but not EC.

Non-Invasive Estimation of Cardiac Index in Healthy Volunteers

The primary objective was to non-invasively measure the cardiac index (CI) and associated haemodynamic parameters of healthy volunteers and their changes with age. This was a single centre, prospective, observational study of healthy volunteers aged between 20 and 59 years, using the ClearSight™ (Edwards Life Sciences, Irvine, CA, USA) device. We recorded 514 observations in 97 participants. The mean CI was 3.5 l/min/m2 (95% confidence interval [95% CI] 3.4 to 3.7 l/min/m2). The mean stroke volume index (SVI) was 47 ml/m2 (95% CI 45 to 49 ml/m2) and the mean systemic vascular resistance index was 2,242 dyne·s/cm5/m2 (95% CI 2,124 to 2,365 dyne·s/cm5/m2). There was an inverse linear relationship between increasing age and CI (P <0.0001), which decreased by 0.044 l/min/m2 (95% CI −0.032 to −0.056 l/min/m2) per year. This change was mostly due to a decrease in SVI of 0.45 ml/m2 (95% CI 0.32 to 0.57 ml/m2) per year (P <0.0001). The mean CI of young healthy humans is approximately 3.5 l/min/m2 and declines by approximately 40 ml/min/m2 per year, mostly due to a decline in stroke volume (SV). These findings have significant implications regarding the clinical interpretation of haemodynamic parameters and the application of these results to individual patients.

Stroke Volume estimation using aortic pressure measurements and aortic cross sectional area: Proof of concept

Accurate Stroke Volume (SV) monitoring is essential for patient with cardiovascular dysfunction patients. However, direct SV measurements are not clinically feasible due to the highly invasive nature of measurement devices. Current devices for indirect monitoring of SV are shown to be inaccurate during sudden hemodynamic changes. This paper presents a novel SV estimation using readily available aortic pressure measurements and aortic cross sectional area, using data from a porcine experiment where medical interventions such as fluid replacement, dobutamine infusions, and recruitment maneuvers induced SV changes in a pig with circulatory shock. Measurement of left ventricular volume, proximal aortic pressure, and descending aortic pressure waveforms were made simultaneously during the experiment. From measured data, proximal aortic pressure was separated into reservoir and excess pressures. Beat-to-beat aortic characteristic impedance values were calculated using both aortic pressure measurements and an estimate of the aortic cross sectional area. SV was estimated using the calculated aortic characteristic impedance and excess component of the proximal aorta. The median difference between directly measured SV and estimated SV was -1.4ml with 95% limit of agreement +/- 6.6ml. This method demonstrates that SV can be accurately captured beat-to-beat during sudden changes in hemodynamic state. This novel SV estimation could enable improved cardiac and circulatory treatment in the critical care environment by titrating treatment to the effect on SV.

Applications of Noninvasive Hemodynamic Monitoring in Obstetric Management

Clinicians managing obstetric patients are dependent on valid hemodynamic measurements to guide care. Heart rate and noninvasive blood pressure guide most current care. New hemodynamic monitors are being used to report research findings and are being investigated by clinicians for their value to supplement standard monitoring. These include arterial pulse contour analysis, Doppler velocimetry, and bioimpedance among others. This chapter serves to present these new devices with a critical review of their advantages and limitations, and most importantly the validity of their measurements.

Cardiac output Optimisation following Liver Transplant (COLT) trial: study protocol for a feasibility randomised controlled trial

Background

Patients with liver cirrhosis undergoing liver transplantation have a hyperdynamic circulation which persists into the early postoperative period making accurate assessment of fluid requirements challenging. Goal-directed fluid therapy (GDFT) has been shown to reduce morbidity and mortality in a number of surgery settings. The impact of GDFT in patients undergoing liver transplantation is unknown. A feasibility trial was designed to determine patient and clinician support for recruitment into a randomised controlled trial of GDFT following liver transplantation, adherence to a GDFT protocol, participant withdrawal, and to determine appropriate endpoints for a subsequent larger trial to evaluate the efficacy of GDFT in patients undergoing liver transplantation.

Methods

The Cardiac output Optimisation following Liver Transplant (COLT) trial is designed as a prospective, single-centre, randomised controlled study to assess the feasibility and safety of GDFT in liver transplantation for patients with cirrhosis. Consenting adults (aged between 18 and 80 years) with biopsy-proven liver cirrhosis who have been selected to undergo a first liver transplantation will be included in the trial and randomised into GDFT or standard care starting immediately after surgery and continuing for the first 12 h thereafter. Both groups will have cardiac output and stroke volume monitored using the FloTrac (EV1000) device. The intervention will consist of a protocolised GDFT approach to patient management, using stroke volume optimisation. The control group will receive standard care, without stroke volume and cardiac output measurement. After 12 h the patient’s fluid management will revert to standard of care. The primary endpoint of this study is feasibility. Secondary endpoints will include a safety assessment of the intervention, graft and patient survival, liver function, postoperative complications graded by Clavien-Dindo criteria, length of intensive care and hospital stay and quality of life across the intervention and control groups.

Discussion

There is a growing body of evidence that the use of perioperative GDFT in surgical patients can improve outcomes; however, signals of harm have also been detected. Patients with liver cirrhosis undergoing liver transplantation have markedly different cardiovascular physiology than general surgical patients. If GDFT is proven to be feasible and safe in this patient group, then a multicentre trial to demonstrate efficacy and cost-effectiveness will be required.

Trial registration

International Standard Randomised Controlled Trial Registry, ID: ISRCTN10329248. Registered on 4 April 2016.

Electronic supplementary material

The online version of this article (10.1186/s13063-018-2488-8) contains supplementary material, which is available to authorized users.

A preliminary study evaluating cardiac output measurement using Pressure Recording Analytical Method (PRAM) in anaesthetized dogs

Background

Haemodynamic variations normally occur in anaesthetized animals, in relation to the animal status, administered drugs, sympathetic and parasympathetic tone, fluid therapy and surgical stimulus. The possibility to measure some cardiovascular parameters, such as cardiac output (CO), during anaesthesia would be beneficial for both the anaesthesia management and its outcome. New techniques for the monitoring of CO are aimed at finding methods which are non invasive, accurate and with good trending ability, which can be used in a clinical setting. The aim of this study was to compare the Pressure Recording Analytical Method (PRAM) with the pulmonary artery thermodilution (TD) for the measurement of cardiac output in 6 anaesthetized critically ill dogs.

Results

Fifty-four pairs of CO measurements were obtained with a median (range) of 3.33 L/min (0.81–7.21) for PRAM-CO and 3.48 L/min (1.41–6.56) for TD-CO. The Bland-Altman analysis showed a mean bias of 0.17 L/min with limits of agreement (LoA) of − 0.46 to 0.81 L/min. The percentage error resulted 18.2%. The 4-quadrant plot analysis showed an acceptable concordance (93%) between the 2 methods. The polar plot showed a good trending ability with the mean angular bias of 3.9° and radial LoA ± 12.1°.

Conclusions

The PRAM resulted in good precision, acceptable concordance and good trending ability for the measure of CO in the anaesthetized dog, representing a promising alternative to thermodilution for the measurement of CO. Among all the pulse contour methods available on the market it is the only one that does not require any calibration or adjustment of the measurement. Further studies are required to verify the ability of this method to accurately measure cardiac output even during unstable hemodynamic conditions.

Comparative Evaluation of Crystalloid Resuscitation Rate in a Human Model of Compensated Haemorrhagic Shock

Introduction:

The most effective rate of fluid resuscitation in haemorrhagic shock is unknown.

Methods:

We performed a randomized crossover pilot study in a healthy volunteer model of compensated haemorrhagic shock. Following venesection of 15 mL/kg of blood, participants were randomized to 20 mL/kg of crystalloid over 10 min (FAST treatment) or 30 min (SLOW treatment). The primary end point was oxygen delivery (DO₂). Secondary end points included pressure and flow-based haemodynamic variables, blood volume expansion, and clinical biochemistry.

Results:

Nine normotensive healthy adult volunteers participated. No significant differences were observed in DO₂ and biochemical variables between the SLOW and FAST groups. Blood volume was reduced by 16% following venesection, with a corresponding 5% reduction in cardiac index (CI) (P < 0.001). Immediately following resuscitation the increase in blood volume corresponded to 54% of the infused volume under FAST treatment and 69% of the infused volume under SLOW treatment (P = 0.03). This blood volume expansion attenuated with time to 24% and 25% of the infused volume 30 min postinfusion. During fluid resuscitation, blood pressure was higher under FAST treatment. However, CI paradoxically decreased in most participants during the resuscitation phase; a finding not observed under SLOW treatment.

Conclusion:

FAST or SLOW fluid resuscitation had no significant impact on DO₂ between treatment groups. In both groups, changes in CI and blood pressure did not reflect the magnitude of intravascular blood volume deficit. Crystalloid resuscitation expanded intravascular blood volume by approximately 25%.

Cardiac Output Monitoring: Validation Studies-how Results Should be Presented

Purpose of Review

Cardiac output monitors can be assessed by a variety of techniques, but a common principle is quantifying agreement between a reference standard and new monitor. The current standard analysis technique is a Bland-Altman plot. The Bland-Altman plot evaluates bias between mean differences of cardiac output, from which an agreement interval is derived. These limits are, however, statistical limits of agreement and the clinical acceptability will depend upon context and application. This article provides suggestions for understanding and presenting the results of cardiac output validation, using standard metrology alongside proposals for criteria used to accept new techniques.

Recent Findings

Confusion about the appropriate way to report “precision” in method comparison studies stem from a lack of clarity on how single or repeated measurements should be interpreted. During serial measurements of cardiac output the true value changes, thus measurement should be considered as serial rather than repeated. Method agreement based upon precision achieved by cardiac output monitors needs to consider each method’s general variability around true values obtained and this data should be generated and presented as part of each study design.

Summary

Studies should report serial measurements from two techniques for cardiac output monitoring. Results of similar techniques from other studies may not always be transferred and compared. Bias and intervals of agreement should be presented as Bland-Altman plots with dynamic cardiac output trends in polar plots. Percentage error should be calculated to allow appropriate comparison of techniques for study populations with different expected cardiac output values.

The Inspired Sinewave Technique: A Comparison Study With Body Plethysmography in Healthy Volunteers

The inspired sinewave technique is a noninvasive method to measure airway dead space, functional residual capacity, pulmonary blood flow, and lung inhomogeneity simultaneously. The purpose of this paper was to assess the repeatability and accuracy of the current device prototype in measuring functional residual capacity, and also participant comfort when using such a device. To assess within-session repeatability, six sinewave measurements were taken over two-hour period in 17 healthy volunteers. To assess day-to-day repeatability, measurements were taken over 16 days in 3 volunteers. To assess accuracy, sinewave measurements were compared to body plethysmography in 44 healthy volunteers. Finally, 18 volunteers who experienced the inspired sinewave device, body plethysmography and spirometry were asked to rate the comfort of each technique on a scale of 1–10. The repeatability coefficients for dead space, functional residual capacity, and blood flow were 48.7 ml, 0.48L, and 2.4L/min respectively. Bland-Altman analyses showed a mean BIAS(SD) of −0.68(0.42)L for functional residual capacity when compared with body plethysmography. 14 out of 18 volunteers rated the inspired sinewave device as their preferred technique. The repeatability and accuracy of functional residual capacity measurements were found to be as good as other techniques in the literature. The high level of comfort and the non-requirement of patient effort meant that, if further refined, the inspired sinewave technique could be an attractive solution for difficult patient groups such as very young children, elderly, and ventilated patients.

Time to correct the flow of corrected flow time

Recently published study of Ma et al. evaluates two relatively novel measures of fluid responsiveness, carotid blood flow and corrected carotid flow time (ccFT). Both measures have been recently quoted as possibly useful, technically simple, and noninvasive dynamic tools in predicting fluid responsiveness. Recently, more research interest has been focused on ccFT and, intrigued by the data presented in this study, we discuss here the impact of the data presented in the paper of Ma et al. to the significance of this metric as a potential tool in the assessment of fluid responsiveness.

Improved pressure contour analysis for estimating cardiac stroke volume using pulse wave velocity measurement

BACKGROUND

Pressure contour analysis is commonly used to estimate cardiac performance for patients suffering from cardiovascular dysfunction in the intensive care unit. However, the existing techniques for continuous estimation of stroke volume (SV) from pressure measurement can be unreliable during hemodynamic instability, which is inevitable for patients requiring significant treatment. For this reason, pressure contour methods must be improved to capture changes in vascular properties and thus provide accurate conversion from pressure to flow.

METHODS

This paper presents a novel pressure contour method utilizing pulse wave velocity (PWV) measurement to capture vascular properties. A three-element Windkessel model combined with the reservoir-wave concept are used to decompose the pressure contour into components related to storage and flow. The model parameters are identified beat-to-beat from the water-hammer equation using measured PWV, wave component of the pressure, and an estimate of subject-specific aortic dimension. SV is then calculated by converting pressure to flow using identified model parameters. The accuracy of this novel method is investigated using data from porcine experiments (N = 4 Pietrain pigs, 20-24.5 kg), where hemodynamic properties were significantly altered using dobutamine, fluid administration, and mechanical ventilation. In the experiment, left ventricular volume was measured using admittance catheter, and aortic pressure waveforms were measured at two locations, the aortic arch and abdominal aorta.

RESULTS

Bland-Altman analysis comparing gold-standard SV measured by the admittance catheter and estimated SV from the novel method showed average limits of agreement of ±26% across significant hemodynamic alterations. This result shows the method is capable of estimating clinically acceptable absolute SV values according to Critchely and Critchely.

CONCLUSION

The novel pressure contour method presented can accurately estimate and track SV even when hemodynamic properties are significantly altered. Integrating PWV measurements into pressure contour analysis improves identification of beat-to-beat changes in Windkessel model parameters, and thus, provides accurate estimate of blood flow from measured pressure contour. The method has great potential for overcoming weaknesses associated with current pressure contour methods for estimating SV.

Thoracic electrical bioimpedance versus suprasternal Doppler in emergency care

OBJECTIVE

There are a number of cardiac output (CO) monitors that could potentially be used in the ED. Two of the most promising methods, thoracic electrical bioimpedance and suprasternal Doppler, have not been directly compared. The aim of this study was to investigate the feasibility of CO monitoring using suprasternal Doppler and bioimpedance in emergency care and compare haemodynamic data obtained from both monitors.

METHODS

Haemodynamic measurements were made on the same group of patients using bioimpedance (Niccomo, Medis, Germany) and suprasternal Doppler (USCOM, Sydney, Australia).

RESULTS

Usable CO data were obtained in 97% of patients by suprasternal Doppler and 87% by bioimpedance. The median CO obtained by Doppler was 3.4 L/min lower than bioimpedance. The stroke volume median was lower by 51 mL in Doppler.

CONCLUSIONS

These two methods of non-invasive cardiac monitoring are not interchangeable. The results suggest that the choice of non-invasive cardiac monitor is important, but the grounds on which to make this choice are not currently clear.

The Trend of Perioperative Care of Gastrectomy in Kanagawa, Japan

Comprehensive surveys on perioperative care in Japan, including that in community or private hospitals, have not been reported, and current trends remain unclear. The present survey was designed to investigate current routines for perioperative care in patients who undergo surgery for gastric cancer in Kanagawa, Japan. A questionnaire was designed specifically to obtain information on perioperative routines in patients with gastric cancer throughout Kanagawa. A total of 55 hospitals in Kanagawa responded. Most hospitals perform antimicrobial prophylaxis every 3 hours intraoperatively, use a postoperative drainage tube, use a urinary catheter for only 2 days after surgery, administer epidural anesthesia, and encourage early mobilization. Liquid intake until 3 hours before surgery is not allowed in most hospitals. Most hospitals do not routinely provide preoperative nutrition support, perform bowel mechanical preparation, administer prophylaxis against thromboembolism, place a postoperative nasogastric tube, attempt to maintain normovolemia, or administer planned nonsteroidal anti-inflammatory drugs. The day of restarting drinking or eating varies considerably. Many elements of perioperative management, especially postoperative oral nutrition, have yet to be standardized for patients with gastric cancer in Japan. There are great gaps between clinical practice and evidence-based practice in fluid management and drain usage.

Early hemodynamic assessment and treatment of elderly patients in the medical ICU

BACKGROUND AND OBJECTIVES

The aim of this retrospective study was to analyze differences in the initial hemodynamic assessment and its impact on the treatment in patients aged 80 years or older compared to younger patients during the first 6 h after admission to the medical intensive care unit (ICU).

RESULTS

We analyzed 615 consecutive patients admitted to the medical ICU of which 124 (20%) were aged 80 years or more. The older group had a significantly higher acute physiology and chronic health evaluation (APACHE II) score, an overall mortality in the ICU and a presence of pre-existing cardiac disease. Both groups did not differ in the presence of shock and shock types on admission. In 57% of older and in 56% of younger patients, transthoracic echocardiography was performed with a higher therapeutic impact in the older patients. Transesophageal echocardiography was performed in 3% of the patients in both groups for specific diagnostic problems. Early reassessment with transthoracic echocardiography was necessary in 5% of the older and in 6% of the younger patients and resulted in a change of the treatment in one third of the patients. Continuous invasive hemodynamic monitoring was used in 11% of the older and in 10% of the younger patients and resulted in a therapeutic change in 71% of the older and in 64% of the younger patients.

CONCLUSION

Patients aged 80 years or older represent 20% of all admissions to the medical ICU. Once admitted the older patients were similarly hemodynamically assessed as the younger ones with a similar impact on the treatment.